1. Field of the Invention
The present invention relates to a storage system having a cooling unit, a storage system control method and a storage system control apparatus.
2. Description of the Related Art
A storage system operated as a RAID (redundant array of independent disks) using plural storage devices has such a structure in which two or more modules are mounted to double the functions. Also, a configuration including a cooling unit to discharge the heat of the disk array unit is disclosed in Japanese Patent Application Laid-Open Nos. 2007-179655 and 10-283125. This configuration also has plural cooling fans and modules for controlling the cooling fans to double the functions.
Incidentally, in controlling the cooling fan, the output of the cooling fan is desirably changed in accordance with the heating value as disclosed by Japanese Patent Application Laid-Open No. 2003-345465 and Japanese Patent Application National Publication No. 2002-518979. As these cooling fans, a multistage fan, for example, controlled by PWM (pulse width modulation) is used. After fully starting the device firmware and determining a control master controller module, the control operation is performed by generating the fan rotation speed control pulse in accordance with a command of the firmware of the control module (CM).
In the prior art, however, the fan rotation speed cannot be controlled before the firmware is fully started and the control master controller module is determined. During the time from the DC power on of the apparatus to the firmware start, therefore, the fan rotation speed cannot be set.
The fan rotation is controlled from each controller module by PWM. As long as the control master CM is not determined, the control frequency of each controller module CM cannot be synchronized. An attempt to control the rotation speed in multiple stages, therefore, would imbalance the rotation speed and cause a swell. As a result, the hardware control is limited to two values of the maximum speed rotation (100% in duty factor) and the fan rotation stop (0% in duty factor).
In a case where the fan rotation stop mode (0% in duty factor) is set by hardware control, the heat cannot be discharged from the apparatus. In a high temperature environment of the apparatus, therefore, the start fault may be caused, and therefore, the fan rotation stop cannot be set by hardware control. In the presently available RAID, the fan is set to the maximum rotation speed (100% in duty factor) by hardware control before the control master CM is determined. Although the heat can be discharged from the apparatus, the fan rotation noise poses a problem.
In one proposed solution, like in the high-end RAID, for example, a module management controller (MMC) driven by a resident power supply in a different system than the DC power-on input is used to monitor the apparatus status before DC power on, and the fan rotation speed is controlled to an optimum rotation speed before determining the control master CM. Since the addition of MMC is required, however, this method harbors the problem of an increased package space and an increased cost.